(Several days late as we decided to go and see Avengers: Age of Ultron, and I didn't have anything queued up.)

Also known as scrying, specifically by water (which, unsurprisingly, is also called hydromancy). According to Wikipedia this can include the study of the ripples produced by pebbles dropped in a pool, along with some other more complicated methods involving drops of oil, rings shaken in bottles, or speaking words over a glass of water and studying its "spontaneous ebullience".

Hydromancy was apparently forbidden in Renaissance magic, along with geomancy, palmistry, divination by fire or weather, divination by bones - specifically shoulder blades (scapulimancy), and necromancy. It's not clear if divination by other parts of the body was acceptable, or why shoulder blades were so offensive. Demonology was also banned.